The present invention relates to a bulldozer apparatus for a working vehicle comprising a vertically pivotable arm assembly, a blade attached to the arm assembly to be pivotable about a fore and aft axis, and a hydraulic cylinder for causing pivotal movement of the blade.
In a conventional working vehicle having a bulldozer apparatus, the blade and the arm assembly are interconnected through a fore and aft axis and a linkage disposed at a right or left side of the fore and aft axis, and a single cylinder is provided for causing pivotal movement of the blade, as disclosed in Japanese Patent Publication No. 53-9445.
The known bulldozer apparatus, however, has the disadvantage of high cost with a great strength required of the fore and aft axis since a reaction force occurring when the vehicle moves backward or forward in an earth moving operation concentrates not only on the linkage but also on the position of attachment of the fore and aft axis having a complicated construction. A further drawback is noted when carrying out an excavating operation with the blade instead of outriggers placed in contact with the ground. The hydraulic pressure of the cylinder is locked adjacent the piston rod and at the bottom thereof at this time but, when the vehicle oscillates sideways under reaction forces of the excavation, the inside pressure at the piston rod end of the cylinder tends to increase over the inside pressure at the bottom thereof. Consequently, a relief tends to occur with a hydraulic circuit connected to the piston rod end of the cylinder, which may result in the danger of an inadvertent tilting of the vehicle.